Rate of Building 7's Fall

WTC 7's Facade Plunged at a Nearly Free-Fall Rate

One of several features of the total collapse of WTC Building 7
that is common in controlled demolitions
is the rapid descent of the building.
Several videos captured the descent of WTC 7's facade from the north.
A
video taken from West Street
about 1000 feet from the building
shows the north facade in considerable detail as it descends.
The following montage was created using frames from that video
separated by one-half second intervals.

facade movement

free-fall

frame

seconds

displacement, floors

displacement, feet

seconds

displacement, feet

difference, feet

0

0.0

0

0.0

-0.65

0.0

0.0

1

0.5

0

0.0

-0.15

0.0

0.0

2

1.0

0.2

6.0

0.35

2.0

-4.0

3

1.5

1.0

12.0

0.85

11.6

-0.4

4

2.0

2.4

28.8

1.35

29.2

-0.4

5

2.5

4.5

54.0

1.85

54.8

+0.8

6

3.0

7.3

87.6

2.35

88.4

+0.8

7

3.5

10.7

128.4

2.85

130.0

+1.6

8

4.0

14.2

170.4

3.35

179.6

+9.2

The table above contains data on the downward displacement
of the northwestern corner of WTC 7 over the period of four seconds
shown in the image slices comprising the montage.
The red rulers superimposed on the image slices demarcate floors.
Displacements were measured by comparing the rulers
to the roof of the white building in the foreground.
The displacements in feet were computed from the displacements in floors
using the estimated floor spacing of 12 feet.
The error margin in placing and reading the rulers is about 3 feet.

The displacement of an obect in free-fall is shown in columns
to the right of those showing the facade movement.
The free-fall distances at the half-second intervals
are based on the object being released 0.15 seconds after
the time coordinate of the second image slice.

The rightmost column gives the free-fall distances
minus the facade displacements.
The differences are within the estimated margin of error
for the facade displacement measurements
for all but the first and final frames.
This shows that
the facade of WTC 7 accelerated downward at very close
to the rate of free-fall in at least its first three seconds of descent,